1. Field of the Invention
The invention relates to a tubing carried perforating gun having an insulation jacket for use in a subterranean well.
2. Brief Description of the Prior Art
During the completion or workover of a subterranean oil or gas well, a casing conduit is run into the well subsequent to the drilling thereof and is cemented into place. In order to provide a passageway for production of the fluid hydrocarbons from one or more production zones within the subterranean well, it is necessary to perforate the metallic casing to provide openings communicating with passageways through the zone for production of the hydrocarbon fluids therethrough. In such instance, a perforating "gun", well known to those skilled in the art is utilized. Such gun may be introduced into the well on a tubular conduit, such as a workstring, or in the case of a permanent completion incorporating the perforating gun, a production conduit. Typically, the perforating gun will have immediately thereabove a percussion actuated firing head for firing of the gun. The firing head/gun assembly may be introduced into the well below a permanent or retrievable bridge plug or packer. The packer is set immediately above the zone to be perforated and the gun may be fired in numerous ways known to those skilled in the art. For example, a heavy bar may be introduced through the tubing string to drop upon the firing pin of the firing head to initiate the chain of events that ultimately results in the gun being firing. Alternatively, the firing head may be activated by variation in tubing and/or annulus pressure, or may be electrically o acoustically activated.
The perforating gun may incorporate a number of configurations and normally will have a series of radially extending longitudinally spaced shaped charges which, when fired, shoot holes through the casing.
As wells are drilled to deeper depths, along the order of 20 to 30 thousand feet, and more, the temperatures encountered are increased substantially and have been known to adversely affect the actuation devices of either the firing head and/or perforating gun.
During the running of perforating guns into the well, particulate matter in the form of cuttings and other debris may interfere with the running of the perforating gun on the tubing into the well during the completion operation. A substantial collection of such debris at a point of deviation in the well bore can result in differential sticking of the gun and/or tubing relative to the casing such that manipulation of the tubing must be effected to unstick the gun at that particular point, thus necessitating considerable and additional rig time and delaying the completion of the well.